The present invention relates to an electric through-wall terminal having a housing and a contact device provided with at least one plug zone for accommodating a test- and/or connection plug. A test plug or else a connection plug or else a test- and connection plug may be inserted into the plug zone. It is also possible for the test- and/or connection plug to act as a short-circuiting plug.
In the prior art a great variety of through-wall terminals have become known comprising a plug zone for accommodating a test- and/or connection plug.
These through-wall terminals tend to be configured as series terminals or test terminal blocks, comprising conductor terminal elements and associated power bars wherein the conductor terminal elements are in contact with one another in a contact area, unless a test plug had been inserted.
These through-wall terminals with connecting and disconnecting options are often employed in circuitry, measuring and control technology. The connecting and disconnecting option at the electric series terminal allows to realize different functions and different test options by way of inserting different plugs or connection plugs. The plugs used may, other than simple connection plugs or through connections, in particular be test plugs. These test plugs may comprise special components which allow testing the proper function of the power circuit connected with the through-wall terminal. Optionally, different test plugs allow to simultaneously or sequentially test different functions.
In the case of through-wall terminals configured as disk-shaped, electric series terminals, they may be plugged together with other electric terminals to form a series terminal block. Then a number of test plugs corresponding to the number of the series terminals can be plugged into such a series terminal block. It is possible to form a test plug block to be plugged into the series terminal block as a whole.
In DE 10 2006 052 894 A1, a test terminal block made of electric series terminals has become known comprising a plug-in zone in every series terminal for inserting a test plug. This known series terminal is provided with a pair of contact areas formed of contact legs in the plug zone for accommodating the contact plug wherein in the normal state the contact legs are in contact with one another in the first contact area, while the contact legs are spaced apart in the second contact area. When inserting a test plug the connection plug contacts the second contact area first. When inserting a test plug it first contacts the second contact area, establishing a test connection. Only inserting further makes the test plug contact the first contact area, urging apart the contact legs which are in resilient contact with one another.
Such a configuration ensures that in such a series terminal the test plug first safely establishes contact with the second contact area prior to disconnecting the electric connection at the first contact area. The known prior art operates reliably.
Testing or maintenance work in switch cabinets or electric system housings often does not require to open the switch cabinet to perform tests. In many cases it is sufficient for example for a through-wall terminal, being a terminal having a plug-in zone for a test plug at the switch cabinet, to be accessible from the exterior, to readily test the state of the electric circuit by inserting a test plug. In these cases it is very advantageous for such a through-wall terminal to be attached accessible on the outside surface of the switch cabinet. The drawback of this is though that in other, more extensive or basic test- and/or maintenance work the through-wall terminal provided with a plug zone for a test plug is disposed on the outside of the switch cabinet housing even when the switch cabinet is open. This results in increased maintenance efforts if the switch cabinet door must be opened since the maintenance worker must then always plug in the test plug from the outside of the switch cabinet although he may have to perform a great deal of maintenance in the interior of the switch cabinet.